We will continue to study the role of the central nervous system in the control of body fluid homeostasis and cardiovascular dynamics. Specific projects on thirst will focus on; 1) establishing whether ablations of the lateral parabrachial nucleus and the area postrema produce overdrinking by the same mechanism; 2) determine if overdrinking produced in animals with lesions of the lateral parabrachial nucleus is due to an alteration of information arising from high and/or low pressure barorecptors. Studies in the control of vasopressin secretion will examine; 1) afferent projects to vasopressin magnocellular neurons and 2) the neurotransmitters that are responsible for activating magnocellular neurons to angiotensin II and to systemically-applied hypertonic saline. The role of catecholamines in the mediation of pressor and drinking responses will be investigated in structures along the lamina terminalis. Following depletion of catecholamines with 6-hydroxydopamine, amine levels will be supplemented within this region to determine if recovery of function can be established. Finally, we will continue to study animals instrumented to measure regional hemodynamics, heart rate and blood pressure while they are behaving. We are particularly interested in investigating the nature of cardiovascular "signatures" during aversive or stressful environmental and psychosocial situations.